The present invention relates to a receiver for receiving broadcast waves and a method of receiving broadcast waves, and more particularly to a receiver and a method for receiving waves, both for use in a broadcasting system in which analog broadcast waves and digital broadcast waves are transmitted in adjacent frequency bands.
In the AM (Amplitude Modulation) broadcasting and the FM (Frequency Modulation) broadcasting, an analog system is employed wherein the broadcast-wave signals are analog signals though the source audio data to be broadcast is converted to digital data.
If the broadcast-wave signals are digital signals, it will become possible not only to broadcast high-quality audio data, but also to broadcast the audio data added with other data. It will also be possible to enhance the use efficiency of frequencies and accomplish broadcasting through more channels.
To receive digital signals, i.e., the broadcast waves of digital broadcasting, a digital broadcasting receiver must be used in place of an analog broadcasting receiver. In order to achieve smooth shift from the analog broadcasting to the digital broadcasting, it is desired that both the analog broadcasting and the digital broadcasting remain in service for a period of time.
A broadcasting system called IBOC (In Band On Channel) system has been proposed as a broadcasting system that performs both analog broadcasting and digital broadcasting. The IBOC system effects both types of broadcasting by allocating frequencies to the analog broadcasting and digital broadcasting as is illustrated in FIG. 5A.
In FIG. 5A, SA is the analog FM broadcast-wave signal (FM signal), and fRx is the carrier frequency of this signal. To transmit digital broadcast-wave signals SD together with the analog broadcast-wave signal SA, two digital broadcast-wave signals SD are arranged on the sides of the broadcast-wave signal SA, close thereto, respectively. Only one broadcast-wave signal SD may be transmitted along with the analog broadcast-wave signal SA. Generally, the broadcast-wave signal SD represents the program that is identical to the program the broadcast-wave signal represents. In the future, the analog broadcast-wave signal SA will not be transmitted, and only the digital broadcast-wave signals SD will accomplish broadcasting. Alternatively, the frequency domain the broadcast-wave signal SA uses will be utilized for the digital broadcasting. It is estimated that 10 to 15 years will pass until the broadcasting shifts from the analog broadcasting to the digital broadcasting.
Hence, receivers that can serve not only during the shift of broadcasting but also after the shift, i.e., receivers that can receive analog broadcast signals and digital broadcast signals, must be provided, if the listeners want to enjoy both the analog broadcasting and the digital broadcasting.
The power that an analog receiver consumes is about 30 mW, whereas the power a digital receiver consumes is 1 W, more or less. That is, the digital receiver consumes about 30 times as much power as the analog receiver. Thus, a receiver that can receive analog broadcast signals and digital broadcast signals will inevitably consume much power even while receiving analog broadcast signals.
An object of the present invention is to provide a novel receiver and novel method, which can receive analog, broadcast signals and digital broadcast signals.
Another object of the invention is to provide a receiver and method in which the power supply voltage applied to the digital processing circuit only when digital broadcast signals can be received, thereby to reduce power consumption.
Still another object of the invention is to provide a receiver and method which can receive analog broadcast signals and digital broadcast signals and in which it can be accurately determined whether or not digital broadcasting is provided, thereby to reliably select a digital broadcast station.
Another object of this invention is to provide a receiver and method for receiving analog broadcast signals and digital broadcast signals, which can reliably select an analog broadcast station.
To attain these objects, the present invention provides a receiver for use in a broadcasting system in which analog broadcast signals and digital broadcast signals are transmitted in adjacent frequency bands. The receiver has an analog processing circuit for receiving and processing analog broadcast-wave signals to extract audio signals; a digital signal processing circuit for receiving and processing digital broadcast-wave signals to extract audio signals; a changeover circuit for selecting either the audio signals supplied from the analog processing circuit or the audio signals supplied from the digital signal processing circuit; a control circuit for controlling the application of an operating power-supply voltage to the digital processing circuit; and a detecting circuit for detecting that a digital broadcast station has been selected. The control circuit applies the operating power-supply voltage to the digital processing circuit only when the detecting circuit detects that a digital broadcast station has been selected.
This invention also provides a receiver for use in a broadcasting system in which analog broadcast signals and digital broadcast signals are transmitted in adjacent frequency bands. The receiver has a circuit for selecting a station in accordance with an analog broadcast-wave signal, an analog processing circuit for receiving and processing analog broadcast-wave signals to extract audio signals; a digital signal processing circuit for receiving and processing digital broadcast-wave signals to extract audio signals; a changeover circuit for selecting either the audio signals supplied from the analog processing circuit or the audio signals supplied from the digital signal processing circuit; a control circuit for controlling the application of an operating power-supply voltage to the digital processing circuit; and a detecting circuit for detecting that a digital broadcast station has been selected. The control circuit applies the operating power-supply voltage to the digital processing circuit only when the detecting circuit detects that a digital broadcast station has been selected. When the detecting circuit does not detect that a digital broadcast station has been selected, the control circuit stops applying the operating power-supply voltage to the digital processing circuit.
Further, the present invention provides a receiver for use in a broadcasting system in which analog broadcast signals and digital broadcast signals are transmitted in adjacent frequency bands. The receiver has a circuit for selecting a station in accordance with an analog broadcast-wave signal, an analog processing circuit for receiving and processing analog broadcast-wave signals to extract audio signals; a digital signal processing circuit for receiving and processing digital broadcast-wave signals to extract audio signals; a changeover circuit for selecting either the audio signals supplied from the analog processing circuit or the audio signals supplied from the digital signal processing circuit; a control circuit for controlling the application of an operating power-supply voltage to the digital processing circuit; and a detecting circuit for detecting that a digital broadcast station has been selected. The control circuit applies the operating power-supply voltage to the digital processing circuit only when the circuit for selecting a station cannot receive analog broadcast waves at the time of selecting a station and when the detecting circuit detects that a digital broadcast station has been selected. When the detecting circuit does not detect that digital broadcast signals are received, the control circuit stops applying the operating power-supply voltage to the digital processing circuit.
Moreover, the invention provides a receiver for use in a broadcasting system in which analog broadcast signals and digital broadcast signals are transmitted in adjacent frequency bands. The receiver has a circuit for selecting a station in accordance with a digital broadcast-wave signal, an analog processing circuit for receiving and processing analog broadcast-wave signals to extract audio signals; a digital signal processing circuit for receiving and processing digital broadcast-wave signals to extract audio signals; a changeover circuit for selecting either the audio signals supplied from the analog processing circuit or the audio signals supplied from the digital signal processing circuit; a control circuit for controlling the application of an operating power-supply voltage to the digital processing circuit; and a detecting circuit for detecting that a digital broadcast station has been selected. The control circuit applies the operating power-supply voltage to the digital processing circuit only when the circuit for selecting a station receives digital broadcast waves and detects that a digital broadcast station has been selected, at the time of selecting a station. When the detecting circuit receiving digital broadcast waves does not detect that digital broadcast signals are received, the control circuit stops applying the operating power-supply voltage to the digital processing circuit.
Still further, this invention provides a receiving method for use in a broadcasting system in which analog broadcast signals and digital broadcast signals are transmitted in adjacent frequency bands. In the method, analog broadcast-wave signals are received at the time of selecting a station, to determine whether or not a digital broadcast station has been selected. Only when it is determined that a digital broadcast station has been selected, an operating power-supply voltage is applied to a digital processing circuit that processes the digital broadcast-wave signals which have been received and extracts audio signals. When it is not determined that a digital broadcast station has been selected, the application of the operating power-supply voltage to the digital processing circuit is stopped.
Furthermore, the present invention provides a receiving method for use in a broadcasting system in which analog broadcast signals and digital broadcast signals are transmitted in adjacent frequency bands. In this method, digital broadcast-wave signals are received at the time of selecting a station. Only when it is determined that a digital broadcast station has been selected, an operating power-supply voltage is applied to a digital processing circuit that processes the digital broadcast-wave signals which have been received and extracts audio signals. When it is not determined that a digital broadcast station has been selected, the application of the operating power-supply voltage to the digital processing circuit is stopped.
The other objects of the invention and the specific advantages resulting from the invention will be more clearly understood from the following description of the embodiments.